scholarly journals Speed-Dependent Reductions of Force Output in People With Poststroke Hemiparesis

1999 ◽  
Vol 79 (10) ◽  
pp. 919-930 ◽  
Author(s):  
David A Brown ◽  
Steven A Kautz
Keyword(s):  
Lower Extremity ◽  
Muscle Activity ◽  
Mechanical Work ◽  
Elderly Subjects ◽  
Electromyographic Activity ◽  
Vastus Medialis ◽  
Force Output ◽  
Paretic Side ◽  
Vastus Medialis Muscle ◽  
Work Done

Abstract Background and Purpose. Movement is slow in people with poststroke hemiparesis. Moving at faster speeds is thought by some researchers to exacerbate of abnormal or unwanted muscle activity. The purpose of this study was to quantify the effects of increased speed on motor performance during pedaling exercise in people with poststroke hemiparesis. Subjects. Twelve elderly subjects with no known neurological impairment and 15 subjects with poststroke hemiparesis of greater than 6 months' duration were tested. Methods. Subjects pedaled at 12 randomly ordered workload and cadence combinations (45-, 90-, 135-, and 180-J workloads at 25, 40, and 55 rpm). Pedal reaction forces were used to calculate work done by each lower extremity. Electromyographic activity was recorded from 7 lower-extremity muscles. Results. The main finding was that net mechanical work done by the paretic lower extremity decreased as speed increased in all subjects. The occurrence of inappropriate muscle activity on the paretic side, however, was not exacerbated in that the vastus medialis muscle on the paretic side did not show a consistent further increase in its prolonged activity at higher speeds. The mechanics of faster pedaling resulted in greater net negative mechanical work because, at higher pedaling rates, the prolonged vastus medialis muscle activity is present during a greater portion of the cycle. Conclusion and Discussion. The lessened force output by the paretic limb is mainly the result of the inherent mechanical demands of higher-speed pedaling and not due to exacerbation of impaired neural control.

Lower-Extremity Muscle Activity During Aquatic and Land Treadmill Running at the Same Speeds

2014 ◽  
Vol 23 (2) ◽  
pp. 107-122 ◽  
Author(s):  
W. Matthew Silvers ◽  
Eadric Bressel ◽  
D. Clark Dickin ◽  
Garry Killgore ◽  
Dennis G. Dolny
Keyword(s):  
Lower Extremity ◽  
Outcome Measures ◽  
Muscle Activity ◽  
Tibialis Anterior ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Swing Phase ◽  
Treadmill Running ◽  
Vastus Medialis ◽  
Lower Extremity Muscle

Context:Muscle activation during aquatic treadmill (ATM) running has not been examined, despite similar investigations for other modes of aquatic locomotion and increased interest in ATM running.Objectives:The objectives of this study were to compare normalized (percentage of maximal voluntary contraction; %MVC), absolute duration (aDUR), and total (tACT) lower-extremity muscle activity during land treadmill (TM) and ATM running at the same speeds.Design:Exploratory, quasi-experimental, crossover design.Setting:Athletic training facility.Participants:12 healthy recreational runners (age = 25.8 ± 5 y, height = 178.4 ± 8.2 cm, mass = 71.5 ± 11.5 kg, running experience = 8.2 ± 5.3 y) volunteered for participation.Intervention:All participants performed TM and ATM running at 174.4, 201.2, and 228.0 m/min while surface electromyographic data were collected from the vastus medialis, rectus femoris, gastrocnemius, tibialis anterior, and biceps femoris.Main Outcome Measures:For each muscle, a 2 × 3 repeated-measures ANOVA was used to analyze the main effects and environment–speed interaction (P ≤ .05) of each dependent variable: %MVC, aDUR, and tACT.Results:Compared with TM, ATM elicited significantly reduced %MVC (−44.0%) but increased aDUR (+213.1%) and tACT (+41.9%) in the vastus medialis, increased %MVC (+48.7%) and aDUR (+128.1%) in the rectus femoris during swing phase, reduced %MVC (−26.9%) and tACT (−40.1%) in the gastrocnemius, increased aDUR (+33.1%) and tACT (+35.7%) in the tibialis anterior, and increased aDUR (+41.3%) and tACT (+29.2%) in the biceps femoris. At faster running speeds, there were significant increases in tibialis anterior %MVC (+8.6−15.2%) and tACT (+12.7−17.0%) and rectus femoris %MVC (12.1−26.6%; swing phase).Conclusion:No significant environment–speed interaction effects suggested that observed muscle-activity differences between ATM and TM were due to environmental variation, ie, buoyancy (presumed to decrease %MVC) and drag forces (presumed to increase aDUR and tACT) in the water.

What Is the Influence of Cambered Running Surface on Lower Extremity Muscle Activity?

2013 ◽  
Vol 29 (4) ◽  
pp. 421-427 ◽  
Author(s):  
Birgit Unfried ◽  
Arnel Aguinaldo ◽  
Daniel Cipriani
Keyword(s):  
Lower Extremity ◽  
Muscle Activity ◽  
Tibialis Anterior ◽  
Gluteus Medius ◽  
Biceps Femoris ◽  
Road Surface ◽  
Vastus Medialis ◽  
Lateral Gastrocnemius ◽  
Lower Extremity Muscle ◽  
Fitness Sport

Running on a road for fitness, sport, or recreation poses unique challenges to the runner, one of which is the camber of the surface. Few studies have examined the effects of camber on running, namely, kinematic studies of the knee and ankle. There is currently no information available regarding muscle response to running on a cambered road surface. The purpose of this study was to investigate the effects of a cambered road on lower extremity muscle activity, as measured by electromyography in recreational runners. In addition, this study examined a true outdoor road surface, as opposed to a treadmill surface. The mean muscle activity of the tibialis anterior, lateral gastrocnemius, vastus medialis oblique, biceps femoris, and gluteus medius were studied. Fifteen runners completed multiple running trials on cambered and level surfaces. During the stance phase, mean activities of tibialis anterior, lateral gastrocnemius, and vastus medialis oblique were greater on the gutter side than the crown side. There were no differences in mean muscle activity during the swing phase. The findings of this study suggest that running on a road camber alters the activity of select lower extremity muscles possibly in response to lower extremity compensations to the cambered condition.

Muscle activities of lower extremity and erector spinae muscles according to ankle joint position during squat exercise

2021 ◽  
pp. 1-6
Author(s):  
Ha-Rim Sung ◽  
Se-Jung Oh ◽  
Jun-Nam Ryu ◽  
Yong-Jun Cha
Keyword(s):  
Lower Extremity ◽  
Ankle Joint ◽  
Muscle Activity ◽  
Vastus Lateralis ◽  
Plantar Flexion ◽  
Erector Spinae ◽  
Neutral Position ◽  
Vastus Medialis ◽  
Joint Position ◽  
Squat Exercise

OBJECTIVE: The purpose of this study was to investigate the most effective ankle joint position for squat exercise by comparing muscle activities of lower extremity and erector spinae muscles in different ankle joint positions. METHODS: Thirty-seven normal healthy adults in their 20s participated in this study. Muscle activities of dominant vastus medialis oblique, vastus lateralis, biceps femoris, and erect spinae were measured in three ankle joint positions; dorsiflexion, neutral, and plantar flexion. RESULTS: Muscle activities of the vastus medialis oblique, vastus lateralis, and erector spinae muscles were statistically different in the three ankle joint positions during squat exercise (p< 0.05). Vastus medialis oblique muscles showed higher muscle activity in ankle plantar flexion than in the dorsiflexion or neutral positions (plantar flexion > neutral position, +3.3% of maximal voluntary isometric contraction (MVIC); plantar flexion > dorsiflexion, +12.2% of MVIC, respectively). Vastus lateralis muscles showed 7.1% of MVIC greater muscle activity in the neutral position than in dorsiflexion, and erector spinae muscles showed higher muscle activity in dorsiflexion than in plantar flexion or in the neutral position (dorsiflexion > neutral position, +4.3% of MVIC; dorsiflexion > plantar flexion, +7.1% of MVIC, respectively). CONCLUSION: In squat exercises designed to strengthen the vastus medialis oblique, ankle joint plantar flexion is probably the most effective ankle training position, and the dorsiflexion position might be the most effective exercise for strengthening the erector spinae muscle.

scholarly journals Patellar Kinematics, Part I: The Influence of Vastus Muscle Activity in Subjects With and Without Patellofemoral Pain

2000 ◽  
Vol 80 (10) ◽  
pp. 956-964 ◽  
Author(s):  
Christopher M Powers
Keyword(s):  
Motor Unit ◽  
Unit Activity ◽  
Muscle Activity ◽  
Knee Flexion ◽  
Patellofemoral Pain ◽  
Vastus Medialis ◽  
Patellar Kinematics ◽  
Motor Unit Activity ◽  
Longus Muscle ◽  
Vastus Medialis Muscle

Abstract Background and Purpose. Reduced motor unit activity of the vastus medialis muscle relative to the vastus lateralis muscle has been implicated as a cause of lateral patellar subluxation. The purpose of this study was to assess the influence of vastus muscle motor unit activity on patellar kinematics. Subjects. Twenty-three women (mean age=26.8 years, SD=8.5, range=14–46) with a diagnosis of patellofemoral pain and 12 women (mean age=29.1 years, SD=5.0, range=24–38) without patellofemoral pain participated. Only female subjects were studied because of potential biomechanical differences between sexes. Methods. Patellar kinematics (kinematic magnetic resonance imaging) and vastus muscle electromyographic (EMG) activity using indwelling electrodes were measured during resisted knee extension. Measurements of medial and lateral patellar displacement and tilt obtained from magnetic resonance images were correlated with normalized vastus lateralis:vastus medialis oblique muscle and vastus lateralis:vastus medialis longus muscle EMG ratios at 45, 36, 27, 18, 9, and 0 degrees of knee flexion using a stepwise regression procedure. Results. The vastus lateralis:vastus medialis longus muscle EMG ratio contributed to the prediction of lateral patellar displacement at 27 degrees of knee flexion (r=−.48), with increased vastus medialis longus muscle activity being associated with greater lateral patellar displacement. A similar inverse relationship was evident with lateral patellar tilt at 36, 27, 18, and 9 degrees of knee flexion. Conclusion and Discussion. These results suggest that increased motor unit activity of the vastus medialis muscle appears to be associated with abnormal patellar kinematics in women, but it is not necessarily a cause of abnormal patellar kinematics.

scholarly journals Electromyography Assessments of the Vastus Medialis Muscle during Soccer Instep Kicking between Dynamic and Static Stretching

2010 ◽  
Vol 24 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Mohammadtaghi Amiri-Khorasani ◽  
Noor Osman ◽  
Ashril Yusof
Keyword(s):  
Muscle Activity ◽  
High Speed ◽  
Soccer Players ◽  
Vastus Medialis ◽  
Static Stretching ◽  
Warm Up ◽  
Dynamic Stretching ◽  
Significant Difference ◽  
Ball Velocity ◽  
Vastus Medialis Muscle

Electromyography Assessments of the Vastus Medialis Muscle during Soccer Instep Kicking between Dynamic and Static StretchingThe purpose of this study was to examine the effects of static and dynamic stretching within a pre-exercise warm-up on vastus medialis muscle activity during instep kicking and ball velocity in soccer players. The kicking motions of dominant legs were captured from using six synchronized high-speed infra-red cameras at 200 Hz and Electromyography at 100 Hz. There was significant difference in vastus medialis activity after dynamic stretching relative to no stretching condition (0.12 ± 0.06 mV) versus static stretching relative to no stretching condition (-0.21 ± 0.10 mV) with p < 0.001). In addition, there was also a significant difference in ball velocity after dynamic stretching relative to no stretching condition (4.53 ± 2.10 m/s) versus static stretching relative to no stretching condition (-1.48 ± 2.43 m/s) with p < 0.003. We concluded that dynamic stretching during the warm-up, as compared to static stretching, is probably more effective as preparation for optimal muscle activity and finally have high ball velocity which is required in soccer.

scholarly journals The Effect of Shoe Type and Load Carrying on Electromyographic Activity of Lower Extremity Muscles during Stair Ascent and Descent

2019 ◽  
Vol 5 (2) ◽  
pp. 92-101
Author(s):  
Nader Farahpour ◽  
◽  
Mahdi Majlesi ◽  
Mohammad Reza Hoseinpouri ◽  
◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Lower Extremity ◽  
Muscle Activity ◽  
The Body ◽  
Emg Activity ◽  
Load Factor ◽  
Electromyographic Activity ◽  
Stair Ascent ◽  
Load Carrying ◽  
Cartilage Wear

Objective Stair ascent and descent is an essential movement task in daily life in which individuals are subjected to repetitive impact forces. The purpose of this study was to evaluate the intensity of Electromyographic (EMG) activity in lower extremity muscles of healthy young men during stair ascent and descent task wearing different type of shoes and carrying loads. Methods Nine men with a mean age of 25.94±3.26 years, mean height of 174±7.4 cm, and mean weight of 70.95±8.25 kg were selected. Four stairs were fabricated and the electromyographic activity of their lower extremity muscles (two muscles in the posterior leg and three quadriceps muscles) in the right side of the body was measured using the 16-channel EMG system MA300 during the task. These tests were conducted in two conditions of with and without load carrying. The load was a cube-shaped box weighing 15% of the body weight. Three cases of footwear were set: barefoot, athletic shoes, and formal shoes. Repeated measure ANOVA was used for data analysis at the significant level of P<0.05. Results The load factor had a significant effect on the intensity of muscle activity. The intensity of muscle activity during ascending stairs was higher than that during descending. In stair descent task, the EMG activity of the vastus medialis muscle was greater than that of the vastus lateralis and rectus femoris muscles, which causes the patella to be pulled inward more leading to patellofemoral articular cartilage wear in the long term. Conclusion Stair ascent puts more pressure on the ankle and knee joints. When carrying the load up stairs, the use of proper shoes can greatly reduce the intensity of muscle activity and delay fatigue. It is, therefore, recommended that people with patellofemoral articular cartilage wear should not use the stairs, if possible.

scholarly journals Is the Occurrence of the Sticking Region in Maximum Smith Machine Squats the Result of Diminishing Potentiation and Co-Contraction of the Prime Movers among Recreationally Resistance Trained Males?

2021 ◽  
Vol 18 (3) ◽  
pp. 1366
Author(s):  
Roland van den Tillaar ◽  
Eirik Lindset Kristiansen ◽  
Stian Larsen
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Gluteus Maximus ◽  
Knee Extensors ◽  
Force Output ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Prime Movers ◽  
Almost All ◽  
Height Data

This study compared the kinetics, barbell, and joint kinematics and muscle activation patterns between a one-repetition maximum (1-RM) Smith machine squat and isometric squats performed at 10 different heights from the lowest barbell height. The aim was to investigate if force output is lowest in the sticking region, indicating that this is a poor biomechanical region. Twelve resistance trained males (age: 22 ± 5 years, mass: 83.5 ± 39 kg, height: 1.81 ± 0.20 m) were tested. A repeated two-way analysis of variance showed that Force output decreased in the sticking region for the 1-RM trial, while for the isometric trials, force output was lowest between 0–15 cm from the lowest barbell height, data that support the sticking region is a poor biomechanical region. Almost all muscles showed higher activity at 1-RM compared with isometric attempts (p < 0.05). The quadriceps activity decreased, and the gluteus maximus and shank muscle activity increased with increasing height (p ≤ 0.024). Moreover, the vastus muscles decreased only for the 1-RM trial while remaining stable at the same positions in the isometric trials (p = 0.04), indicating that potentiation occurs. Our findings suggest that a co-contraction between the hip and knee extensors, together with potentiation from the vastus muscles during ascent, creates a poor biomechanical region for force output, and thereby the sticking region among recreationally resistance trained males during 1-RM Smith machine squats.

scholarly journals Effects of Functional Electrical Stimulation Cycling of Different Duration on Viscoelastic and Electromyographic Properties of the Knee in Patients with Spinal Cord Injury

2020 ◽  
Vol 11 (1) ◽  
pp. 7
Author(s):  
Antonino Casabona ◽  
Maria Stella Valle ◽  
Claudio Dominante ◽  
Luca Laudani ◽  
Maria Pia Onesta ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Muscle Activity ◽  
Response Times ◽  
Electromyographic Activity ◽  
Functional Changes ◽  
Pendulum Test ◽  
Cord Injury

The benefits of functional electrical stimulation during cycling (FES-cycling) have been ascertained following spinal cord injury. The instrumented pendulum test was applied to chronic paraplegic patients to investigate the effects of FES-cycling of different duration (20-min vs. 40-min) on biomechanical and electromyographic characterization of knee mobility. Seven adults with post-traumatic paraplegia attended two FES-cycling sessions, a 20-min and a 40-min one, in a random order. Knee angular excursion, stiffness and viscosity were measured using the pendulum test before and after each session. Surface electromyographic activity was recorded from the rectus femoris (RF) and biceps femoris (BF) muscles. FES-cycling led to reduced excursion (p < 0.001) and increased stiffness (p = 0.005) of the knee, which was more evident after the 20-min than 40-min session. Noteworthy, biomechanical changes were associated with an increase of muscle activity and changes in latency of muscle activity only for 20-min, with anticipated response times for RF (p < 0.001) and delayed responses for BF (p = 0.033). These results indicate that significant functional changes in knee mobility can be achieved by FES-cycling for 20 min, as evaluated by the pendulum test in patients with chronic paraplegia. The observed muscle behaviour suggests modulatory effects of exercise on spinal network aimed to partially restore automatic neuronal processes.

scholarly journals Crystallization of Polymers under the Influence of an External Force Field

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2078
Author(s):  
Rajdeep Singh Payal ◽  
Jens-Uwe Sommer
Keyword(s):  
External Force ◽  
Melting Behavior ◽  
Mechanical Work ◽  
Stem Length ◽  
Heat Of Fusion ◽  
Strong Increase ◽  
Lamellar Thickness ◽  
Equilibrium System ◽  
External Force Field ◽  
Work Done

We simulated the crystallization and melting behavior of entangled polymer melts using molecular dynamics where each chain is subject to a force dipole acting on its ends. This mimics the deformation of chains in a flow field but represents a well-defined equilibrium system in the melt state. Under weak extension within the linear response of the chains, the mechanical work done on the system is about two orders of magnitude smaller as compared with the heat of fusion. As a consequence, thermodynamic and simple arguments following the secondary nucleation model predict only small changes of the crystalline phase. By contrast, an increase of the stem length up to a factor of two is observed in our simulations. On the other hand, the lamellar thickening induced by the external force is proportional to the increase of the entanglement length in the melt prior to crystallization as measured by the primitive path method. While the mechanical work done on the system is only a small perturbation for thermodynamics of polymer crystallization, the change of the primitive path is large. This suggests that a strong increase in the lamellar thickness induced, by external deformation, a topological rather than a thermodynamic origin.

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